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- [ S IGN IN ] Anatomy & Physiology (Open + Free) Sy lla bu s Unit 10:: The Respiratory System Introduction to the Respiratory Sy stem Module 38 / Respiratory Structures and Functions | Ou t lin e | Help | Mor e This course is not led by an instructor Respiratory Lev els of Organization Search this course Gross Anatomy and the Upper Respiratory Tract Identify and describe gross & m icroscopic anatom y of the respiratory tract and related organs. Upper Respiratory Tract Nose The external portion of the nose begins at the base of the frontal bone and extends over the maxilla, with the nasal bone providing the bridge of the nose. Extending from the nasal bone is a collection of hyaline cartilages that make up the bulk of the nose. The medial region of the nose consists of a central septal cartilage with two lateral processes. The tip of the nose contains the major alar cartilage. Two minor alar cartilages are found at the sides and base of the lateral septal cartilages. Dense fibrous connective tissue is found under the skin of the sides lateral aspects the nose, away from the cartilage. Variations in the size of a person’s nose, or its form, are due to differences in the various cartilages. The visible nose is actually the entryway into the nasal cavity, where the major functions of the nose occur. The openings to the nose, the nares, are lined with coarse hairs to aid in filtration of particulate matter. The area immediately inside the nares, the vestibule, contains a large number of sebaceous glands, sweat glands, and hair follicles. By The Em irr (Diagram of Nose) CC-BY-3 .0 Nose. This work by K. Larson is licensed under a Creativ e Com m ons Attribution 3 .0 United States 325 (http://creativ ecom m ons.org/licenses/by /3 .0/us/). The nasal cavity is divided into right and left sides by the nasal septum. This dividing wall’s anterior portion is made of cartilage; bone contributed by the vomer and part of the ethmoid bones of the skull make up the posterior. The roof of the nasal cavity consists of parts of the ethmoid and sphenoid bones. Its floor, the palate, forms the roof of the mouth. It is separated into the hard and soft palate. The anterior hard palate is formed from the maxillary process of the palatine bone. The posterior soft palate does not contain bone and moves during swallowing to close off the nasal cavity to prevent material from entering it from the mouth. Extending from the nasal septum are three pairs of C-shaped structures called conchae. The superior, middle, and inferior conchae extend the length of the nasal cavity. They are covered by a mucus membrane that contains a large number of mucus-secreting cells and blood vessels. A bloody nose highlights the richness of the blood supply to the membranes on the conchae. The conchae serve as baffles to increase the surface area of the nasal cavity. The mucus glands and blood vessels aid in humidifying and warming the air coming into the body. There are two types of epithelial coverings in the nasal cavity: respiratory epithelium and olfactory epithelium. Both types of epithelia appear very similar when viewed through a light microscope. The olfactory mucosa found in the roof of the cavity detects odors. This epithelial layer contains specialized nerve cells that detect odors and transmit impulses to the first cranial nerve. The respiratory epithelium that covers the rest of the nasal cavity is also found through most of the respiratory tract and is pseudostratified, ciliated, columnar epithelia. Paranasal sinuses Within the bones surrounding the nasal cavity are paranasal sinuses (a sinus is a hollow area), which function to make the skull lighter as well as moisten and warm incoming air. These sinuses frequently become filled with excess fluid when a person has a head cold. Since the paranasal sinuses serve as resonators for speech and sound it is not surprising that the sound of the voice becomes altered when they are filled with fluid or swollen. The frontal, sphenoid, ethmoid and maxillary bones all contain sinus cavities. did I get this Pharynx As the air passes posteriorly through the nasal cavity, it enters the pharynx. This structure encompasses three distinct areas and connects the nasal passage to the larynx in the throat. It extends about 13 centimeters or 5 inches from the base of the skull to the level of the sixth cervical vertebrae. The wall of all three portions contains two layers of skeletal muscle. The inner layer is arranged in a circular pattern, and the outer layer is arranged longitudinally. Nasopharynx The superior section of the pharynx is called the nasopharynx. It is posterior to the nasal cavity and inferior to the sphenoid bone. This chamber shares the same epithelia as the nasal cavity and acts only as a conduit for air. The other two portions of the pharynx contain shared passages with the digestive tract and act as conduits for both air and food. The nasopharynx closes off during swallowing by raising the soft palate. Also found in this area are structures associated with immune system. The paired pharyngeal tonsils, also known as the adenoids, lie in the posterior wall of the nasopharynx. Oropharynx The second portion of the pharynx is the oropharynx. It runs from the soft palate to the epiglottis and is posterior to the oral cavity. The opening from the oral cavity to the oropharynx is called the oropharyngeal isthmus (Isthmus of Fauces). A difference between the nasopharynx and oropharynx is the epithelial covering of the passages. In comparison to the nasopharynx, which is lined with columnar epithelia, the oropharynx is covered by stratified squamous epithelia, that are often found covering areas which are subject to a great deal of frictional wear. The many layers of epithelial cells serve to protect the underlying tissues from being damaged by the food and material coming into the passage from the mouth. Laryngopharynx The third portion of the pharynx is the laryngopharynx. The shortest of the three parts of the pharynx, it runs inferiorly from epiglottis and ends superior to the esophagus. The laryngopharynx carries both air and food and is lined with stratified sqaumous epithelia. did I get this Tonsils The paired pharyngeal tonsils, also known as the adenoids, lie in the posterior wall of the nasopharynx. The other tonsils, the tubal tonsils, protect the auditory tubes and middle ear against entering microorganism. They are located at the opening of the tube that connects the middle ear to the nasopharynx. The auditory or Eustachian tube equilibrates air pressures between the environment and the middle ear. The orientation of the auditory tube changes during infancy and early childhood. The tube is oriented horizontally until around age two. Consequently, it frequently serves as a point of entry for bacteria in children less than two years of age. Around age two, the auditory tube changes course and slants down from the ear, allowing fluid to drain more readily. Without the fluid to act as a growth medium and conduit to the middle ear, older children usually experience few ear infections. The paired palatine tonsils lie along the two sides of the Isthmus of Fauces in the oropharynx. The lingual (lingual meaning tongue) tonsils are not in the oropharynx, but are located at the base of the tongue. Collectively, the tonsils aid in filtering foreign material that could do harm. Tonsils. did I get this Larynx After air leaves the pharynx, it enters the larynx, a complex structure that extends from the laryngopharynx and the hyoid bone to the trachea. It is about 5 cm (2 in.) long. In addition to providing a passageway for air, the larynx directs air and food to their appropriate tubes. The airway is blocked by closing off the opening of the trachea with the epiglottis upon swallowing. The vocal cords, which are used in making sound and speech, can be found within the larynx. The epithelial lining of the larynx exhibits two different arrangements. Initially stratified squamous epithelia lines from the laryngopharynx to the vocal cords. Inferior to the vocal cords the epithelial lining shifts to pseudostratified, ciliated, columnar epithelia. The nine cartilage structures found in the larynx provide key anatomical landmarks. They function to maintain an open airway. Eight of the cartilages are composed of hyaline cartilage. Detail of Lary nx. This work by Cenv eo is licensed under a Creativ e Com m ons Attribution 3 .0 United States (http://creativ ecom m ons.org/licenses/by /3 .0/us/). Epiglottis The epiglottis is made of elastic cartilage and covered with stratified squamous epithelia. It connects loosely to the tongue, the hyoid bone, and the rim of the thyroid cartilage. The epiglottis is normally open, allowing air to freely flow into the rest of the larynx and the trachea. When a person swallows, the front of the epiglottis is raised, and the posterior portion descends, covering the glottis, which is the opening to the vocal cords and trachea. This movement directs food and water to the esophagus and prevents it from entering the bottom portion of the larynx and the upper trachea. If someone tries to talk or laugh and swallow at the same time, the air used to talk or laugh forces the epiglottis open, the swallowed material “goes down the wrong tube,” and choking results. Thyroid cartilage The thyroid cartilage is the largest of the cartilages of the larynx and is found at the front of the larynx. In the fetus the cartilage originates as two separate plates that fuse before birth. This roughly triangularly shaped cartilage contains the laryngeal prominence, commonly known as the “Adam’s apple”. The laryngeal prominence becomes more prominent in males during puberty as the larynx widens and the voice deepens. The thyroid cartilage connects to the hyoid bone by the thyrohyoid membrane or ligament. Cricoid cartilage Inferior to the thyroid cartilage is the cricoid cartilage. It connects superiorly to the thyroid cartilage by the cricothyroid ligament and inferiorly to the trachea by the cricotracheal ligament. When an occlusion of the upper respiratory tract occurs and a tracheostomy is performed to facilitate breathing, the cricothyroid ligament must be punctured. Arytenoids cartilages, cuneiform cartilages, corniculate cartilages The next six cartilages are found in three pairs. The first pair, the arytenoids cartilages, anchor the true vocal cords. The second pair are the cuneiform cartilages, and the third pair are the corniculate cartilages. All three pairs of cartilages are found in the lateral and posterior walls of the larynx. Except for the epiglottis, the arrangement of the cartilages of the larynx ensure that the passages through the larynx remain open. Vocal cords Two pairs of folded tissue can be observed in the larynx immediately inferior to the epiglottis. These are the false and true vocal cords respectively. The false vocal cords do not function in making sounds or speech but aid in closing the glottis, which opens to the rest of the larynx and the respiratory system. Below the false vocal cords are the true vocal cords. The true cords run from the arytenoids to the thyroid cartilage. They are reinforced with elastic fibers and vibrate when adequate air is forced through the gap between them, resulting in sound. Pitch control is achieved by adjusting the tension on the cords. Lessening the tension lowers the pitch. During puberty in males the cords are usually lengthened making for a deeper sound. Actual speech is achieved with the coordination of muscles in the pharynx, face, tongue, soft palate, and lips. did I get this Upper Respiratory By Arcadian (Head and Neck) Open Learning Initiativ e Unless otherwise noted this work is licensed under a Creativ e Com m ons Attribution 3 .0 Unported License. 325